ui: Cleanup class/struct forward declarations

components/previews/core/previews_opt_out_store_sql.cc

Index: components/previews/core/previews_opt_out_store_sql.cc
diff --git a/components/previews/core/previews_opt_out_store_sql.cc b/components/previews/core/previews_opt_out_store_sql.cc
index 6feb4a16ffa5ed3a4f0d7d8b6cca03d52efae9ee..a6fe9e7ea690cdba8274d72cbb8c90c75c69e98f 100644
--- a/components/previews/core/previews_opt_out_store_sql.cc
+++ b/components/previews/core/previews_opt_out_store_sql.cc
@@ -4,14 +4,18 @@
 
 #include "components/previews/core/previews_opt_out_store_sql.h"
 
+#include <string>
+
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sequenced_task_runner.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/previews/core/previews_black_list.h"
 #include "components/previews/core/previews_black_list_item.h"
@@ -25,18 +29,36 @@ namespace previews {
 
 namespace {
 
+// Command line switch to change the previews per row DB size.
+const char kMaxRowsPerHost[] = "previews-max-opt-out-rows-per-host";
+
+// Command line switch to change the previews DB size.
+const char kMaxRows[] = "previews-max-opt-out-rows";
+
+// Returns the maximum number of table rows allowed per host for the previews
+// opt out store. This is enforced during insertion of new navigation entries.
+int MaxRowsPerHostInOptOutDB() {
+  std::string max_rows =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          kMaxRowsPerHost);
+  int value;
+  return base::StringToInt(max_rows, &value) ? value : 32;
+}
+
+// Returns the maximum number of table rows allowed for the previews opt out
+// store. This is enforced during load time; thus the database can grow
+// larger than this temporarily.
+int MaxRowsInOptOutDB() {
+  std::string max_rows =
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(kMaxRows);
+  int value;
+  return base::StringToInt(max_rows, &value) ? value : 3200;
+}
+
 // This is a macro instead of a const, so it can be used inline in other SQL
 // statements below.
 #define PREVIEWS_TABLE_NAME "previews_v1"
 
-// The maximum number of entries allowed per host. Entries are evicted based on
-// entry time.
-const int kMaxRowsPerHost = 32;
-
-// The maximum number of entries allowed in the data base. Entries are evicted
-// based on entry time.
-const int kMaxRowsInDB = 3200;
-
 void CreateSchema(sql::Connection* db) {
   const char kSql[] = "CREATE TABLE IF NOT EXISTS " PREVIEWS_TABLE_NAME
                       " (host_name VARCHAR NOT NULL,"
@@ -129,8 +151,8 @@ void AddPreviewNavigationToDataBase(sql::Connection* db,
 // Removes entries if per data base row limit is exceeded.
 void MaybeEvictHostEntryFromDataBase(sql::Connection* db,
                                      const std::string& host_name) {
-  // Delete the oldest entries if there are more than |kMaxRowsPerHost| for
-  // |host_name|.
+  // Delete the oldest entries if there are more than |MaxRowsPerHostInOptOutDB|
+  // for |host_name|.
   // DELETE ... LIMIT -1 OFFSET x means delete all but the first x entries.
   const char kSqlDeleteByHost[] = "DELETE FROM " PREVIEWS_TABLE_NAME
                                   " WHERE ROWID IN"
@@ -142,7 +164,7 @@ void MaybeEvictHostEntryFromDataBase(sql::Connection* db,
   sql::Statement statement_delete_by_host(
       db->GetCachedStatement(SQL_FROM_HERE, kSqlDeleteByHost));
   statement_delete_by_host.BindString(0, host_name);
-  statement_delete_by_host.BindInt(1, kMaxRowsPerHost);
+  statement_delete_by_host.BindInt(1, MaxRowsPerHostInOptOutDB());
   statement_delete_by_host.Run();
 }
 
@@ -151,14 +173,17 @@ void LoadBlackListFromDataBase(
     scoped_refptr<base::SingleThreadTaskRunner> runner,
     LoadBlackListCallback callback) {
   // Gets the table sorted by host and time. Limits the number of hosts using
-  // most recent opt_out time as the limiting function.
+  // most recent opt_out time as the limiting function. Sorting is free due to
+  // the table structure, and it improves performance in the loop below.
   const char kSql[] =
       "SELECT host_name, time, opt_out"
-      " FROM " PREVIEWS_TABLE_NAME;
+      " FROM " PREVIEWS_TABLE_NAME " ORDER BY host_name, time DESC";
 
   sql::Statement statement(db->GetUniqueStatement(kSql));
 
   std::unique_ptr<BlackListItemMap> black_list_item_map(new BlackListItemMap());
+  std::unique_ptr<PreviewsBlackListItem> host_indifferent_black_list_item =
+      PreviewsBlackList::CreateHostIndifferentBlackListItem();
   int count = 0;
   // Add the host name, the visit time, and opt out history to
   // |black_list_item_map|.
@@ -166,8 +191,8 @@ void LoadBlackListFromDataBase(
     ++count;
     std::string host_name = statement.ColumnString(0);
     PreviewsBlackListItem* black_list_item =
-        PreviewsBlackList::GetOrCreateBlackListItem(black_list_item_map.get(),
-                                                    host_name);
+        PreviewsBlackList::GetOrCreateBlackListItemForMap(
+            black_list_item_map.get(), host_name);
     DCHECK_LE(black_list_item_map->size(),
               params::MaxInMemoryHostsInBlackList());
     // Allows the internal logic of PreviewsBlackListItem to determine how to
@@ -176,11 +201,16 @@ void LoadBlackListFromDataBase(
     black_list_item->AddPreviewNavigation(
         statement.ColumnBool(2),
         base::Time::FromInternalValue(statement.ColumnInt64(1)));
+    // Allows the internal logic of PreviewsBlackListItem to determine what
+    // items to evict.
+    host_indifferent_black_list_item->AddPreviewNavigation(
+        statement.ColumnBool(2),
+        base::Time::FromInternalValue(statement.ColumnInt64(1)));
   }
 
   UMA_HISTOGRAM_COUNTS_10000("Previews.OptOut.DBRowCount", count);
 
-  if (count > kMaxRowsInDB) {
+  if (count > MaxRowsInOptOutDB()) {
     // Delete the oldest entries if there are more than |kMaxEntriesInDB|.
     // DELETE ... LIMIT -1 OFFSET x means delete all but the first x entries.
     const char kSqlDeleteByDBSize[] = "DELETE FROM " PREVIEWS_TABLE_NAME
@@ -191,12 +221,13 @@ void LoadBlackListFromDataBase(
 
     sql::Statement statement_delete(
         db->GetCachedStatement(SQL_FROM_HERE, kSqlDeleteByDBSize));
-    statement_delete.BindInt(0, kMaxRowsInDB);
+    statement_delete.BindInt(0, MaxRowsInOptOutDB());
     statement_delete.Run();
   }
 
   runner->PostTask(FROM_HERE,
-                   base::Bind(callback, base::Passed(&black_list_item_map)));
+                   base::Bind(callback, base::Passed(&black_list_item_map),
+                              base::Passed(&host_indifferent_black_list_item)));
 }
 
 // Synchronous implementations, these are run on the background thread